tailieunhanh - Manufacturing Processes phần 7

(Nguồn: Sau khi MC Shaw) chip gián đoạn bao gồm các phân đoạn được sản xuất bởi các vết nứt của kim loại phía trước của công cụ. Các phân đoạn có thể là kết nối lỏng lẻo với nhau hoặc không có liên quan. Chip như vậy là thường xuyên nhất được tìm thấy trong gia công vật liệu dễ vỡ hoặc cắt vật liệu dẻo ở tốc độ rất thấp hoặc góc cào thấp hoặc tiêu cực. | REAMING 13-61 Fig. a Various types of drills and drilling and reaming operations b spade drill c trepanning tool with four cutting-tool inserts. removed to chips the gun drill run at a high speed under a light feed and used to drill small long holes the core drill used to bore out cored holes the oil-hole drill having holes or tubes in its body through which oil is forced to the cutting lips three- and four-fluted drills used to enlarge holes after a leader hole has been cored punched or drilled with a two-fluted drill twist drills made from flat high-speed steel or drop-forged to desired shape and then twisted. Drills are also made of solid carbide or of high-speed steel with an insert of carbide to form the chisel edge and both cutting edges. They are used primarily for drilling abrasive or very hard materials. Drilling Recommendations The most common tool material for drills is high-speed steel M1 M7 and M10. General recommendations for speeds and feeds in drilling a variety of materials are given in Table . Hole depth is also a factor in selecting drilling parameters. A general troubleshooting guide for drilling is given in Table . Table General Troubleshooting Guide for Drilling Operations Problem Probable causes Drill breakage Dull drill drill seizing in hole because of chips clogging flutes feed too high lip relief angle too small Excessive drill wear Cutting speed too high ineffective cutting fluid rake angle too high drill burned and strength lost when sharpened Tapered hole Drill misaligned or bent lips not equal web not central Oversize hole Same as above machine spindle loose chisel edge not central side pressure on workpiece Poor hole surface finish Dull drill ineffective cutting fluid welding of workpiece material on drill margin improperly ground drill improper alignment REAMING A reamer is a multiple-cutting edge tool used to enlarge or finish holes and to provide accurate dimensions as well as good finish. Reamers are of